Conventionally, a fastener for removably mounting a cluster to the instrument panel of a vehicle has been generally formed of metal or plastic. In FIGS. 7 and 8, an assembled state of such a fastener is shown in a cross-sectional view.
The fastener shown in FIG. 7 is one made using a metal spring plate. FIG. 7 shows a conventional use of a metal fastener. As shown in FIG. 7, the fastener 300 is mounted with an insertion rib 322 of a cluster 320 interposed and closely contacted between grippers 310. Further, one of the grippers 310 is provided at one end thereof with an engagement pin 312, which is inserted into a engagement hole 324 of the insertion rib 322. In this manner, when the fastener 300, pre-mounted to the insertion rib 322, is inserted from an outer surface 336 of the instrument panel 330 into a mounting aperture 332 of the instrument panel 330, both opposite shoulder portions 314 of the fastener 300 are engaged with inner edges of the mounting aperture 332 in the inner surface 334 of the instrument panel 330, and simultaneously, an attached surface of the insertion rib 322 is pressed against the outer surface 336 of the instrument panel 330. Thereby, the cluster 320 is fixed to the instrument panel 330.
However, the above conventional fastener 300 has such problems that it is not firmly fixed because its grippers 310 are brought into point contact with the insertion rib 322, and is readily bent or loosened because it is made of metal. Further, while the cluster 320 is manipulated before the mounted fastener 300 is fixed into the mounting aperture 332, the fastener 300 would be separated from the cluster 320. In addition, after the cluster 320 is fixed to the instrument panel 330, a noise would be generated by vibration of the metal fastener.
In order to overcome these problems, the plastic fastener shown in FIG. 8 has been proposed. The fastener 400 of FIG. 8 comprises a fastener body 410 having a U shape, a pair of legs 412 extending in parallel, and a pair of gripper arms 414 extending from the inside of the fastener body 410. Each of the gripper arms 414 has a free end formed with an engagement projection 416. Further, the free ends of the legs 412 are formed with stabilizers 419 protruding outwardly therefrom, respectively.
The pair of gripper arms 414 have flat gripper surfaces 413 formed as opposite inner surfaces. The free ends of the gripper arms 414 are formed with the engagement projections 416 fixed in an engagement slot 424 of an insertion rib 422. The fastener body 410 connected with the pair of legs 412 is formed on both opposite sides thereof with shoulder portions 418 protruding outwardly.
When the fastener 400 is fixed to the insertion rib 422 of a cluster 420, the insertion rib 422 is brought into surface contact between the gripper surfaces 413 of the gripper arms 414, and simultaneously the engagement projections 416 are fixed in the engagement slot 424 of the insertion rib. When the fastener 400 is inserted from an outer surface 436 of the instrument panel 430 into a mounting aperture 432 of an instrument panel 430 after being fixed to the insertion rib 422, the shoulder portions 418 of the fastener 400 are elastically pressed against an inner surface 434 of the instrument panel 430 around the mounting aperture 432 of the instrument panel 430.
In the plastic fastener 400, the insertion rib 422 is thin, and the free ends of the pair of gripper arms 414 are formed with engagement projections 416 fixed in the engagement slot 424 of the insertion rib 422. As such, the engagement projections 416 have difficulty not only in securing the depth at which they enter the engagement slot 424, but also maintaining sufficient engagement force between the engagement projections 416 and the engagement slot 424. Especially, when the cluster 420 is removed from the instrument panel 430 for maintenance or repair, the fastener 400 should be separated from the instrument panel 430 together with the insertion rib 422. However, when the engagement depth between the engagement projections 416 and the engagement slot 424 is not sufficiently provided, the fastener 400 is left on the side of the instrument panel 430, or falls down to the bottom, which leads to confusion during maintenance work.
Further, when the thickness of the insertion rib 422 increases to sufficiently secure the engagement depth, an outer surface of the cluster 420, which is viewed inside the vehicle by any occupant such as a driver, is subjected to a sink by the thickness difference between the insertion rib 422 and a base of the cluster 420 integrally formed with the insertion rib 422. Therefore, such a sink spoils the indoor scenery of the vehicle.